This invention relates to a suction device for an outboard motor and more particularly to an improved induction system for the protective cowling of the power head of an outboard motor.
In connection with outboard motors it is well known that the power head consists not only of an internal combustion engine, but also of a protective cowling assembly which encircles and encloses the engine. It is desirable to provide such a protective cowling both for appearance purposes and also so as to protect components of the engine from the elements and particularly from the water which may splash around from the operation of the associated watercraft. Of course, it is also necessary to provide air inlet openings in the protective cowling so that air can be drawn into the protective cowling for engine operation. Primarily this air is for the induction system of the engine.
Normally it is the practice to provide a cavity in the main housing portion of the protective cowling that is covered by a closure plate but which defines an air inlet opening, which opening normally faces rearward There is then provided a duct in the upper wall of the depressed portion of the main cowling that permits air to flow from this cavity into the interior of the protective cowling for engine operation. The combination of the location of the air inlet opening and the configuration of the duct is chosen so as to try to eliminate the ingestion of water into the interior of the protective cowling while, at the same time, not restricting air flow. The duct must provide sufficient cross sectional area so as to permit adequate air flow. However, as the cross sectional area of the duct is increased, the likelihood of water injection with conventional systems also increases. Furthermore, if the duct is made of a small cross sectional area, then the high flow velocities which result will, in addition to restricting air flow, tend to draw moisture and water into the interior of the protective cowling.
Although the solution to the aforenoted problem may appear to be obvious, this is not actually true. That is, it may be thought that the problem can be solved by employing multiple ducts that extend through the protective cowling for delivering air to the engine. The space requirements of an outboard motor call for the protective cowling to be extremely compact in nature. As a result, the protective cowling frequently has a generally dome like configuration over the fly wheel of the engine and thus does not afford a great deal of area for the provision of additional ducting. Furthermore, because of the spatial requirements, the location of additional ducts gives rise to small inlet openings or restricted flow areas into the duct inlets which can cause high velocity air flow in this area that will draw water into the interior of the protective cowling.
It is, therefore, a principal object of this invention to provide an improved induction system for the protective cowling of an outboard motor.
It is a further object of this invention to provide an induction system and ducting arrangement for the protective cowling of an outboard motor that will insure adequate air flow but which will also insure against the induction of water into the engine area confined by the protective cowling.
It is a further object of this invention to provide an improved arrangement for drawing air through the protective cowling of an outboard motor for engine operation without restricting air flow, inducing high velocity air flows or causing water to enter the engine compartment.